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~ Common Emitter Amplifier ~ Transistor rbb Calculator ~

To be used with a Common Emitter test jig as described Here
Boltzmann Constant — k 1.3806x10-23 J/K    [ Joules/Kelvin ]
Charge on a single Electron — q 1.6022x10-19 C   [ Coulomb or Amperes/sec ]
Measurement device load — RL Ω Parallel with RC assumed a.c. coupled
Collector Resistor — RC Ω Load resistor  [ R& RS assumed = 0 ]
Measured Voltage across RC — VRC V     I= VRC/R= mA
Measured Voltage Gain AVm  [ affected by high rbb and low ro ]
Noise Voltage at Collector — VNtot µVrms  Enter Measured value @ IC T & Bn
Transistor d.c. current gain — β hFE from data sheets @ IC or measured
Device Temperature — T ˚C    Calculation uses  T =  ˚K
Measurement Noise Bandwidth — Bn Hz — Is not the –3dB BW see Here
Calculated results using the values entered above
Voltage Gain neglecting ro — AV V/V = α RC/re 
Emitter Internal Resistance — re Ω = VT/IC     VT = kT/q = 
Load resistor including ro — RCm Ω                     RC || RL Ω
Internal Collector Resistor — ro kΩ              VA = ro • IC V
Noise at Collector due to IC — VNIC µVrms = √2 q IBn  • (RCm–re)
Noise at Collector due to RCm — VNRC µVrms = √4 k T Bn RCm
Noise at Collector due to rbb µV = √V2Ntot–V2NRC–V2NIC = √V2Nrbb+V2NIB
rbb calculated from √V2Nrbb+V2NIB Ω              The –ve result 

Nota BeneThe value of RC modified by ro [RCm] must be less than the total collector load RC || RL ~ The calculated value of rbb must be positive and the negative result negative for the answer to be plausible ~ NaN [Not a Number] may indicate the measured gain or other inputs are not correct or a non numeric input was entered

See also ~ rbb calculated from data–sheet values   but beware some data–sheet figures may not be in the units you need

 

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